Method and device for the representation of an operation area during laser operations

ABSTRACT

The invention relates to a device for the three-dimensional representation of an operation area, in particular an eye, during laser operations, comprising a spatial recording system ( 10 ), an image-processing system ( 15 ) and a spatial display unit ( 20 ).

The present invention relates to a method and a device for therepresentation of an operation area during laser operations.

In ophthalmology, it is known in the case of poor eyesight to shape thecornea by the ablation of tissue. As methods, the so-called PRK(photorefractive keratectomy) and LASIK (laser-assisted in situkeratomileusis) methods have established themselves, in which initiallya small flap of epithelium, Bowman membrane and stroma is cut andunfolded and then the PRK is carried out in the stroma bed.

Lasers of suitable wavelength are used for ablation. The excimer laserwith a wavelength of 193 nm is particularly suitable for this purpose.However, other lasers such as Er:YAG solid-state lasers are also alreadyused for this.

The data for the extent of the defective vision are established by sighttests, by means of refractometers and recently also by the evaluation ofmeasurements of the wavefront. Other methods and devices are also known,which can be used to calculate firing coordinates for the actualoperative procedure from these measurement values.

A laser operation is monitored by the surgeon or doctor usually byobserving the operation area by means of a microscope. The doctor thusobtains a spatial impression of the operation area. However, the viewthrough the microscope allows only one person a spatial impression.

Representation on a monitor etc. by means of a camera is also known.However, in this case the spatial impression of the operation area islost. In the case of an operation using a slit scanner, the progress ofthe operation and the sequence of the ablation steps can be very wellperceived and monitored by the doctor. The doctor can thus detectabnormalities in the ablation process early and counteract these, forexample stop the operation, etc.

With today's modern spot scanners, the ablation process is no longereasy to understand due to various factors. Firstly, the firing frequencyof the lasers is increasing all the time and lies well above theperceptive capability of the surgeon. The ablation process is alsopatient-dependent and the steering and placement of the spot in theablation area is subject to complex algorithms which attempt to solvethe most varied tasks and problems of the ablation process (thermalload, smoke). An ablation algorithm for example breaks down thenecessary firings for a complete correction into many small individualcorrections, with the aim that the operation can be aborted at any timeand it can be guaranteed that an optically satisfactory result isachieved (cf. the valuable contribution to the state of the art in thepatent specification DE 197 27 573). Therefore, in the case of moremodern spot scanners, it is no longer possible for a surgeon to monitorthe complex ablation process—by checking the correct positioning of thelaser beam on the area to be operated on—by “looking through themicroscope”.

The field of vision is also seriously limited when “looking through themicroscope” because of the design. In order to use operation equipment,to ascertain status information or progress information for equipment,the doctor must stop looking through the operation microscope andtherefore take his eyes off the operation area.

When representing the operation area for several observers (teachingpurposes, monitoring etc.), the operation area can be represented bymeans of a camera and a monitor. Because of the principle involved,however, the spatial impression is lost in this case. However, this isof decisive importance during such microsurgical procedures.

The ablation processes in PRK using a spot scanner are so complex thatthe doctor is scarcely in a position to tell whether the operation isprogressing correctly or to detect, early, problems which arise, so asto act to correct them. In order to control equipment etc., the doctormust take his eyes off the operation area, in order to use the equipmentor to record status information.

It is therefore the aim and object of the invention to make availabledevices and methods which allow the doctor to be able to clearly monitorthe progress of the operation and thus to consciously control theoperation.

This object is achieved by a device according to the independent deviceclaim and also by a method according to the independent method claim.Advantageous further developments are defined in the dependent claims.

In particular, the object is achieved by a device for thethree-dimensional representation of an operation area, in particular aneye, during laser operations, comprising a spatial recording system(10), an image-processing system (15) and a spatial display unit (20).This device makes it possible to three-dimensionally represent theoperation area and to clearly monitor the progress of the operation,even when not looking through the microscope. In particular, in this wayseveral observers can observe the operation area simultaneously, withoutlosing the three-dimensional impression.

The spatial recording system is preferably a camera system, with whichimage information or data of an object can be obtained typically fromseveral observation angles. These data then allow the reconstruction ofa three-dimensional representation of this object, i.e. the operationarea.

The image-processing system evaluates the obtained data and processesthem so that they are suitable for the following spatial display unitfor the representation of a three-dimensional or spatial image. Theimage-processing system can be a chip, a computer, software or amicroprocessor.

The spatial display unit is preferably a 3-D display, a hologram or athree-dimensional representation unit generated by laser. Particularlypreferably, it is an arrangement for three-dimensional representationaccording to DE 198 25 950. The spatial extent of the starting position,i.e. the position before the operative procedure, and also the spatialextent of the position after an operation can be advantageouslyrepresented by means of such a display.

In a preferred embodiment of the present invention, the device accordingto the invention also comprises a control module (30); at least one itemof medical equipment (40) and a bus system which connects the spatialdisplay unit (20) and the control module (30), so that data andinformation can be displayed on the display unit (20). It is herebypossible that additional information relating to the operation or theoperation laser etc. can be displayed by the three-dimensional orspatial representation of the operation area which is to be observed.The surgeon and other observers can thus record valuable additionalinformation without having to take their eyes off the spatiallyrepresented operation area.

The control module is preferably a computer, a calculator, amicrocontroller.

The item of medical equipment preferably comprises an operation laserfor refractive surgery. In addition, further devices such as eyetrackers, online topography sensors, online wavefront sensors,illumination units and also eye identification systems (includingrotation control and identification according to the application DE10052201 of 20.10.2000) can be used. This equipment sends data regardingits own status via the bus system to the control unit and also receivesinstructions from the control device via the bus system. Particularlypreferably, the algorithm for the processing of the operation programand the data of the planned operation are also on the control unit orare fed into this or made available to this.

Data and information are particularly preferably data relating to theoperation area, preferably a laser for refractive corneal surgery (suchas firing rate, energy, pulse shape, etc.) or data regarding theoperation (such as patient data, temperature of the tissue or operationarea, operation time already elapsed, remaining time of the operation,operation laser settings, etc.) or status information (limits of thearea of the eye tracker, limits of the operating range of the laser,progress of the operation, energy status, etc.).

In another preferred embodiment of the present invention, the deviceaccording to the invention also comprises a touch-sensitive displayoverlay. It is thereby possible for the surgeon to input controlcommands or equipment control functions via the touch-sensitive displayoverlay. These can be passed on to the control unit and from there beused to control the medical equipment.

In another preferred embodiment of the present invention, image datarelating to the operation area, additional data and information and alsocontrol panels can be represented on the display unit (20). Thisrepresentation of all relevant and interesting data for the operationmakes it possible for the surgeon to keep his eye on all parameters andcircumstances of the operation, without having to take his eye off thespatially represented operation area. These various data can berepresented as a PIP (picture in a picture) or overlaid. The images anddata can also be displayed in a multi-window technique.

In addition, it is possible to display several different views of theoperation area simultaneously. These can be different observationangles, different perspectives, clips or magnification scales. It isalso possible to represent images of different time domains next to eachother, which is preferable in particular if the chronology of anoperation is to be displayed. This is particularly interesting forteaching events in which the data and the course of previous operationsis to be presented, without foregoing the spatial impression.

In particular panels and symbols, which can be activated by touching thetouch-sensitive display overlay, are provided as control panels. Theseare preferably symbols for controlling a magnification of the image, inparticular for infinitely variable magnification (digital zoom). Cameraguiding symbols for selecting the perspective and the observation angleare also preferably provided, and symbols for selecting from theindividual windows, etc.

A device is quite particularly preferred in which reference data of anideal operation area after the operation, in particular of an idealcornea shape, can be spatially represented on the spatial display unit(20) via an image of the current operation area, in particular of thecurrent cornea. It is thereby possible to represent the data of theideal cornea via the image of the current, curved cornea and thereby toillustrate the difference. During the operation, the manner in which thecornea operated on ever more closely resembles the ideal shaperepresented, and is finally made congruent with it, can be monitoredlive. Additionally, current deviations of the cornea that areestablished online can be compared with the initial correction valuespresently during the operation on the basis of a wavefront analysis andthus an even more precise correction can be illustrated during theactual course of the operation.

The starting position and desired final position can thus be representedsuch that the layer thickness to be ablated within the framework of theoperative procedure (ablation volume) can be seen.

The device according to the invention also preferably has a simulationunit which, upon every single laser firing, realizes on the display anablation which, in terms of location and volume ablation, preciselysimulates the ablation that takes place during the ablation on thecornea. The device according to the invention is designed such that,during an operation, upon each laser firing on the display, a volumeunit that is sufficient for the volume ablation on the eye is removedfrom the display. With the device according to the invention, the courseof the ablation of the cornea can therefore be monitored by the surgeon.

In a preferred version, for every single firing, the coordinates for thevolume removal are measured directly from the scanner on the display. Inthis way, the ablation takes place on the display at precisely the pointwhich corresponds to the respective position of the scanners at thispoint. Should the scanners not assume the precise position, an ablationwith correspondingly modified coordinates also takes place on thedisplay. A greatly improved online control of the course of theoperation by the surgeon is therefore possible by means of the deviceaccording to the invention. At the end of the operation, he can alsorecord in a simple manner the final position that has been realized.

Should the realized final position not wholly correspond to the desiredcorrection, the surgeon can decide whether he will immediately carry outa post-correction. Further coordinates for the ablation can thus becalculated from the realized final position and from the originallydesired position, so that a post-correction can take place immediatelyafterwards.

Coordinates for a post-correction are preferably establishedautomatically, so that the post-correction can be carried outimmediately after the original program. This correction is alsomonitored on the display according to the idea of the invention. Anonline topography of the cornea surface can thus be represented on thespatial display unit.

The simulation unit is preferably also connected to the unit forcontrolling the laser energy. Should the laser energy differ from theproposed value, the simulated volume ablation can also be modifiedaccordingly.

Furthermore, the simulation unit (monitoring unit) can be connected toan online wavefront sensor. The current wavefront of the eye isspatially represented. Through the spatial representation of the presentwavefront of the eye during the operation, the surgeon can directlymonitor the progress and success of the operation on the patient. Due tothe invention, a wavefront which has been modified and differs from theideal wavefront can also be displayed directly. This can arise due tounforeseeable factors during the operation. The spatial representationtherefore makes it possible for the surgeon to make a sound decisiondecide to decide in favour of a further correction under otherparameters (in order to also lead the new wavefront aberrations to anideal wavefront) or to end the operation.

The object of the invention is also achieved by a method according tothe invention for the three-dimensional representation of an operationarea (1), in particular an eye, during laser operations, comprising thesteps: recording of the operation area (1) by means of a spatialrecording system (10), transfer of the information obtained from thepreceding step to an image-processing system (15), processing of theinformation in the image-processing system (15) and representation ofthis processed information on a spatial display unit (20).

The method according to the invention preferably also comprises thestep: representation of additional data on the spatial display unit(20). These data can, as stated above, be data and informationconcerning the patient, the progress of the operation or the medicalequipment, in particular the operation laser.

Particularly preferably, the method according to the invention alsocomprises the steps: registration of control commands, in particular bytouching a touch-sensitive display (25), steering medical equipment (40)in accordance with the registered control commands. These controlcommands can, as stated above, be camera-position and clip-selectioncommands and also control commands which directly relate to theoperation laser (emergency stop, repetition of special sequences,re-calculation, etc.).

The device according to the invention and also the method according tothe invention can be used in particular in the field of ophthalmology.For example, the material processing in the case of contact lenses orintraocular lenses (IOLs) can be monitored with the device according tothe invention or the method according to the invention. As a rule, theprocessing does not take place on or in the eye. The observation of theprocessing procedure during series production of contact lenses orintraocular lenses is also conceivable. The control of the finalposition of the respective lenses is conceivable in particular here asan area of use of the device according to the invention and the methodaccording to the invention.

It is also possible for the patient himself to monitor the production ofa lens, for example an intraocular lens or a contact lens. In this way,he can form an impression beforehand of the chances of success.Monitoring the processing procedure of the individual lenses gives thepatient confidence for the ensuing operation. The processed lens ispreferably reflected in an intermediate image plane of an opticalsystem.

A further possible use of the device according to the invention and themethod according to the invention is the monitoring of the materialprocessing on a contact lens located on the eye. Here, the entireeye/contact lens system can be measured together. The processing takesplace only on the contact lens. The eye itself is not operated on.

The device according to the invention and the method according to theinvention can also be used for non-medical applications. In principle,it is possible to use them in any type of processing of a surface bymeans of a laser.

The invention will be explained further in the following with referenceto drawings. Further advantageous features are described here. There areshown in:

FIG. 1 a schematic representation of a device according to theinvention;

FIG. 2 a schematic representation of a device according to the inventionfor observation for more than one person; and

FIG. 3: a basic representation of the components of an embodiment of adevice according to the present invention.

FIG. 1 shows a schematic representation of a device according to theinvention. A surgeon 0 observes a spatial image 23 of a patient's eyewhich is represented by a display for spatial representation 20. The eyeof the patient 1 is then operated on by means of a laser 45.

FIG. 2 shows a schematic representation of a device according to theinvention for observation for more than one person. Several observers0.1, 0.2 and 0.3 simultaneously observe, by means of only one spatialdisplay unit 20, the spatial image of the eye 23 to be treated.

FIG. 3 shows a basic representation of the components of an embodimentof a device according to the present invention. A spatial recordingsystem 10 is connected to an image-processing system 15. This isconnected to a control module 30. The control module 30 connects medicalequipment 40.1 to 40.n to the spatial display unit 20. A touch-sensitivedisplay overlay 25 is connected to the spatial display unit 20.

This structure according to the invention makes it possible to recordthree-dimensionally an operation area by the spatial recording system10, to process these data via an image-processing system 15 and totransfer this information to the control unit 30. The information of themedical equipment 40.n also meets here. These data are then representedtogether or alone via the spatial display unit 20. Both thethree-dimensional operation area and status data of the medicalequipment 40.n can be displayed here. The touch-sensitive displayoverlay 25 makes it possible for the surgeon to input control commandsand thus either to select views of the operation area (multi-windowtechnique, PIP, etc.), to call up status data or their progress or alsoto control the medical equipment.

The invention relates to a visual device for the spatial representationof the operation area during medical operations—preferably duringoperations on the eye using lasers in order to correct vision defects.

With the invention described here, it is possible to make the operationarea visible on a display and to represent it spatially. The inventionmakes it possible to represent the operation area independently of anoperation microscope for a large number of observers. The operation areacan be represented much larger, any areas can be magnified orrepresented simultaneously as a PIP (picture in picture).

In addition to the more natural representation of the operation area, atthe same time as the operation, information can be faded in orrepresented which is important to the doctor and the process of theoperation and thus allows complete control of the item of equipmentwithout losing sight of the operation area.

The additional integration of a touch-sensitive display therefore allowscomplete process control, control of the item of equipment etc. to takeplace simultaneously.

The present invention therefore represents a solution which makes itpossible, during an operation, to represent the operation area spatiallyon a display for several persons, to fade in any information into theoperation area and to control the item of operation equipment—preferablya laser for refractive corneal surgery.

LIST OF REFERENCE NUMBERS

0 Observer 1 Operation area 10 Spatial recording system 15Image-processing system 20 Spatial display unit 23 Spatialrepresentation of the operation area 25 Touch-sensitive display overlay30 Control module 40 Item of medical equipment 45 Operation laser

1. Device for the three-dimensional representation of an operation area,in particular an eye, during laser operations, comprising a spatialrecording system (10), an image-processing system (15) and a spatialdisplay unit (20). 2-9. (canceled)